Will I be able to hear other traffic talking to ATC?`

Right now, SayIntentions will see other traffic and call out traffic advisories for you if you're under radar services / flight following. However, it won't attempt to sequence you, and you won't hear them, because it has no way to know what the other plane is trying to do. So while it adds some level of immersion (totally worth it), it's not the "full ATC experience".

Put another way — for all "other traffic", we can see heading, altitude, lat/lon, speed, aircraft type...... and that's about it.   It's enough for traffic advisories, but not enough to do much else. (This is an MSFS AND X-Plane limitation).

To solve this, we'll be injecting and controlling our own traffic some time in late 2024. We've got traffic injection working at "proof of concept" level. We can put planes in a pattern, put a line of aircraft on final... and because it's our traffic, we can predict its movement. So we're definitely going to be able to get fully traffic-aware ATC.